More illness in offspring of bipolar patients from the U.S. compared to Europe.

BACKGROUND Evidence suggests that patients with bipolar disorder from the United States have an earlier age of onset and a more difficult course of illness than those from Germany and the Netherlands. These characteristics were related to a greater family burden of psychiatric illness and the experience of more psychosocial adversity in childhood. We hypothesized that this greater illness burden would extend to the offspring of the US patients. METHODS 968 outpatients (average age 41) with bipolar illness gave informed consent for participation in a treatment outcome network and filled out a detailed questionnaire about their illness and family history of illness, including whether their offspring had a diagnosis of depression, bipolar disorder, alcohol or substance abuse, suicide attempt or "other" illness. Of those with children, 356 were from the US and 132 were from Europe. RESULTS Compared to the Europeans, offspring of patients from the US had significantly (p<0.001) more depression, bipolar disorder, drug abuse, and "other" illnesses. The number of illnesses in the offspring was related to the bipolar parent being from the US, having had childhood adversity, more than 20 prior episodes, and more parental psychiatric illness. CONCLUSIONS While the findings are limited by their basis on self report, the distribution of the percentages in the US offspring are similar to those of Axelson et al. (2015) who used direct interviews. The higher burden of illness in the offspring and their in direct progenitors from the US compared to Europe warrant new attempts at better treatment and prevention.